Solubility product constant for slightly soluble salt Assistant Lecturer Hiba Sabah Assistant Lecturer Sura Zuhair Assistant Lecturer Zeina Dawoad

Introduction When slightly soluble electrolyte is dissolved to form saturated solution, the solubility is described by special constant known as solubility product constant Ksp. The aim of this experiment is to determine the Ksp for KHT (potassium acid tartrate). silver chloride (Agcl) is an example of such slightly soluble salt. It is the excess solid in equilibrium with the ion in saturated solution at specific temperature

Factors affecting Ksp 1-Temperature: - Ksp is increased with increasing the temperature. 2- Common ion: - increasing the concentration of any ion in solution is leading to decrease the solubility (except if the ion forms soluble complex with the salt).

Experimental work

Calculation

Ca3(PO4)2(s) ⇌ 3Ca2+(aq) + 2PO43−(aq) We saw that the Ksp for Ca3(PO4)2 is 2.07 × 10−33 at 25°C. Calculate the aqueous solubility of Ca3(PO4)2 in terms of the following: the molarity of ions produced in solution Ca3(PO4)2(s) ⇌ 3Ca2+(aq) + 2PO43−(aq) Ca3(PO4)2 [Ca2+] [PO43−] initial pure solid change — +3x +2x final 3x 2x Answer: [PO43−] = 2.28 × 10−7 and [Ca2+] = 3.42 × 10−7.

The solubility product of silver carbonate (Ag2CO3) is 8 The solubility product of silver carbonate (Ag2CO3) is 8.46 × 10−12 at 25°C. Calculate the following: A- the molarity of a saturated solution B- the mass of silver carbonate that will dissolve in 100 mL of water at this temperature Answer: A- 1.28 × 10−4 M B- 3.54 mg